Motor fuel production



Oct. 15, 1940. G. ARM1sTEAD.JR

y MGTOR FUEL PRODUCTION Filed oct. 25. 1937 mSx A 5%) N. J

BY ra/q MMM ATTORNEY Patented Oct. 15, 1940 UNITED STATES PATENT OFFICE MOTOR FUEL PRODUCTION Application October 23, 1937, Serial No. 170,602

2 Claims.

This invention relates to the treatment of hydrocarbon oil to produce lighter hydrocarbons therefrom. More particularly, the invention relates to the treatment of crude oil or partially topped crude oil to effect conversion thereof to motor fuel and -other valuable products under conditions of highest efliciency with the production of gasoline constituents of high anti-knock value.

m It is an object' of the invention to produce a method of treating a plurality of hydrocarbon oils of varyingboiling ranges, and intermediate products produced from said hydrocarbon oils, separately under -conditions selected for each 1,-, material, to produce therefrom motor-fuel products, and intermediate products suitable for iurther conversion, under conditions selected for each treatment to effect a combined operation of highest efficiency whereby motor fuel of high 20 anti-knock value is produced with minimum production of gas and undesirable heavy products `and deposition of coke.

It is a further object 1of the invention to pro-y vide a method whereby crude oil or partially 25 topped crude oil may be eiliciently treated under the above-described conditions by separating `said oil into various fractions .and treating said lfractions and intermediate products produced therefrom under said separate conditions for maxi- 30 mum over-all efficiency.

y It is ya further object of the invention to provide a process of the above naturewherein heavy naphtha and a relatively heavy hydrocarbon oil such as reduced lcrude are simultaneously tre-ated 35 in combination to efectreiorming Of .the naphtha to produce gasoline constituents of' improved anti-knock value with simultaneous minimum production of gas land the cracking of the reduced crude to produce gasoline constituents of high 40 anti-knock value.

It is a further object of the invention to produce -a method of the labove nature wherein a condensate produced in the system and of relatively great refractoriness is treated in combinaknock value with la minimum requirement of .apparatus- The invention contemplates the treatment substantially in combination o-f a plurality of fractions of hydrocarbon oil of diierent boiling ranges whereby a light fraction, which may be -heavy naphtha, and lan intermediate fraction, which may be a virgin gasoil, are :separately subjected to elevated conditions of temperature a-nd l pressure to effe-ct reforming of the heavy naphtha to produce constituents of improved anti-knock. value, and substantial cracking and conversion of the intermediate fraction to products in the gasoline boiling range. A heavy fraction such as y heavy gas oil or reduced crude is combined with the Vnaphtl'ia fraction after said reforming treatment, andthe thus merged products are subjected to cracking conditions of temperature and pressure to effect cracking of the heavy fraction and conversion thereof to lighter products with addi- 2'0 tional reforming of the heavy naphtha t-o the desired extent. The -combined treatment of the heavy naphtha and heavy hydrocarbon oil Afrac-` Ition may be suitably carried out in a single elongated heating zone of restricted cross section, such as a pipe coil, whereby-the heavier oil is introduced into the coil at an intermediate point .or points selected whereby the heavy naphtha is iirst subjected to the desired reforming conditions of temperature and pressure whereby substantial reforming is effected prior to the admixture therewith of the said heavy hydrocarbon oil. The merged products are thereafter passed through the remainder of the coil under conditions selected to produce the desired cracking of the heavy oil with or without further reforming treatment of the heavy naphtha.

rIlhe said intermediate fraction which may be a virgin gas oil is simultaneously separately subjected to elevated conditions of temperature Iand 40 pressure, for example, in :a separate elongated heating zone of restricted :cross section to effect substantial Icracking and conversion thereof On `a once-through basis to produce therefrom .a maxi- CilA Cil

from a heavy naphtha fraction, which may be combined with the first-mentioned heavy naphtha for reforming treatment therewith, or which may be separately treated.

Condensate separated from the vapors produced from one or both vof the aforementioned cracking treatments is separately subjected to elevated conditions of temperature and pressure, for example, in a third elongated zone of restricted cross section to effect cracking and conversion thereof to lighter products including gas'- oline constituents. the last-mentioned cracking treatment are separated into vapors and liquid residue, and the vapors are fractionated to form therefrom a condensate and a desired distillate. The above-mentioned separation of cracked products may be carried out alone or jointly with the separation of other cracked products in the system. Similarly, the above-mentioned fractionation may be carried out alone or in combination with the fractionation of other vapors produced in the system. Preferably, however, the separation and fractionation of the cracked products from the lastmentioned cracking treatment are carried 4out separately whereby a separate condensate is obtained therefrom. This condensate may be returned to the system for further cracking treatment by combining it with the heavy naphtha prior to the passage thereof to the first-mentioned heating Zone whereby said condensate is subjected to cracking conditions of temperature and pressure during the said reforming treatment to effect conversion thereof to lighter products including gasoline constituents; or the last-mentioned condensate may be combined with the products of cracking from the second-mentioned cracking operation. Conveniently this may be accomplished by using said condensate as a cooling liquid for admixture with'the hot products from said cracking operation whereby the said condensate is combined with said cracked products and recovered as condensate together with the material .of similar boiling point contained in the cracked products; or the condensate may be admixed with the said cracked products by introduction as reflux in the fractionation of the vapors from said cracking treatment; or the said condensate may be admixed with cracked products from any cracking operation in the system from which a similar condensate is collected for passage to the third-mentioned elongated heating zone.

Specifically, the invention contemplates the distillation of crude oil or partially topped crude oil to separate therefrom a light fraction which may be a heavy naphtha, a heavy fraction which may be a reduced crude or a heavy gas oil, and an intermediate fraction having a boiling range intermediate that of the said heavy and light fractions, and the treatment, in combination, of the fractions thus obtained in the manner described above.

The naphtha distillates produced in each cracking treatment may be recovered separately cr in combination, and the gasolines thus obtained may be subjected to any further desir-ed treatment. Separately collected gasoline fractions may be separately treated or may be blended in any desired proportions for further treatment.

The invention will be further described by reference to specific embodiments. It is to be understood, however, that the invention is not limited by such specic reference but is capable of other embodiments within the spirit and scope of the invention.

The cracked products from The accompanying drawing is a ow diagram of an apparatus suitable for carrying out the present invention. The invention will be specifically described by reference to specific embodiments carried out in the apparatus illustrated and by reference to the drawing. It is to be understood, however, that the invention is limited in no way by the drawing but is capable of other embodiments kthan those described `and which may be beyond the physical limitations ofthe apparatus indicated.

Referring to the drawing, crude oil or partially topped crude oil is introduced to the system through line I provided with a pump 2. The crude oil so introduced is heated to a distillation temperature to effect subsequent separation by distillation into vapors and a liquid residue whereby fractions separated from the vapors and the said residue are suitable for further treatment in the system. The preliminary heating of the crude oil may be accomplished by suitable heat exchange with hot products produced within the system or other similar means. In addition to such treatment the crude oil may be heated by passage through an elongated heating zone of restricted cross section such as a coil located in a heater; or the preliminary heating of the crude oil may be accomplished entirely by the last-mentioned means. For purposes of simplicity in illustration the heating of the crude oil is represented in the drawing as being accomplished entirely by passage through a separate heater 3 provided with a suitable coil.

Heater 3 and heaters 4, 5 and 0, whose functions will be described below, are shown as sepz;

arate entities for purposes of illustration. It is to be understood, however, that the functions of these heaters may be performed by several coils each located in a furnace structure which also houses one yor more other coils, the coils being arranged in various parts of the furnace in accordance with the temperatures desired to be imparted to the materials passing through the coils. For example, all of the said coils may be housed in a single furnace structure.

In heater 3 the crude oil is heated to a temperature sumcient to effect subsequent vaporization to the desired degree. For example, the crude oil may be heated in heater 3 to a temperature of 500 to 800 F. at a pressure varying from atmospheric up to 100 pounds per square inch.

The heated crude oil is withdrawn from heater 3 through line 'I and introduced into the lower portion of crude flash tower 8 with or `without reduction in pressure by means of valve S located in line 1. In tower 8 conditions of temperature and pressure are maintained to effect vaporization of constituents boiling at 650 to 750 F. and lower. The resulting reduced crude collects in the bottom of tower 8, and additional heat may be applied at that point to assist in the desired vaporization, for example, by means of a heating coil IIJ.

The vapors ascend tower 8 and are fractionated in the upper portion thereof to effect the separation of heavy constituents therefrom and permit the passage overhead of a vapor consisting of light naphtha constituents and lighter products. Suitable cooling means such as a cooling coil II may be provided in the upper portion of tower 8 to effect the desired fractionation. Trap-out trays I2 and I3 are provided at intermediate points in the tower 8 to collect a heavy naphtha condensate and a gas-oil condensate, respectively. Either or both of these condensate cuts may contain the kerosene fractions usually found between the gasoline and gas oil fractions and the gas oil cut may, under some circumstances, be of substantially a kerosene character. The above-described separation of the crude oil into reduced crude and gas oil and heavy naphtha condensates is for purposes of illustration only. The reduced crude so separated may be used as such in the'process of the invention, or the crude oil may be further distilled to separate therefrom vapors from which a heavy gas-oil condensate may be separated, for example, one having an initial boiling point of 650 to 750 F. 'I'his may be accomplished in a single vaporization step or in a plurality of stages. For example, the reduced crude collected in the bottom of tower 8 may be further distilled by separate means (not shown) such as, for example, by vacuum, to effect the production of a heavy gas-oil condensate which may be used in the modifications of the process of the invention described below in place of the reduced crude referred to therein.

Toeifect the specific separation illustrated, however, tower 8 may be operated at a pressure of atmospheric to 100 pounds per square inch with a bottom temperature of 500 to '750 F. and a top temperature of 250 to 350 F. to effect the passage overhead of a light naphtha distillate and the collection in the bottom of a reduced crude having a gravity of, for example, to 26 A. P. I.

Line I4 connects the trap-out tray I2 and the inlet of thecoil of the heater 4. Pump I5 is provided in line I4 to effect transfer of heavy naphtha from the trap-out tray I2 to the inlet of the coil of heater 4. Line I6 connects the bottom of tower 8 with Aan intermediate point or points of the coil of heater 4 and is provided with a pump I'I to effect the introduction of reduced crude from the bottom of tower 8 into the coil of heater 4 at at least one intermediate point therein. The connection between line I6 and the coil of heater 4 is arranged whereby a substantial portion of the coil lies between the connection and the inlet of the coil whereby the heavy naphtha introduced through line I4 passes through a vsubstantial portion of the coil and may be subjected to the desired elevated conditions of temperature and pressure to effect substantial reforming thereof prior to the admixture therewith of reduced crude introduced through line i6. In that portion of the coil of heater 4 located between the connection with line I4 and the connection with line I6 the hydrocarbon oil passing therethrough is heated to a temperature of 900 to 1l00 F. at a pressure of 200 to 1000 pounds per square inch. For example, it may be heated to a temperature of 1025 F. at 500 pounds per square inch.

The reduced crude may be preheated by suitable means not shown prior to introduction into the coil of heater 4, and its temperature, the proportion thereof introduced and the rate of application of heat to that portion of the coil.

lying between the connection with line I6 and the exit thereof are regulated to effect the desired treatment of the merged products therein. For example, the merged products may be main-4 tained under conditions necessary to effect substantial cracking of the heavier constituents with additional reforming of the naphtha constituents, and that portion of the coil may be maintained at a pressure the same or lower than that obtaining in the portion of the coil lying between the entrance and the connection with line I6, with a nal exit temperature of 800 to 975 F., for example, 900 F. Conveniently, the coil of heater 4 maybe arranged within the furnace housing whereby that portion of the coil through which the merged products pass lies in a cooler portion of the furnace and functions as a soaking section for the reforming treatment as well as for the cracking of the reduced crude in the combined section.

The outlet of the coil of heater 4 is connected by line I8 with the lower portion of evaporator I9 whereby the cracked products from heater 4 may be'introduced into evaporator I9 with or without any desired `reduction in pressure by means of valve 20 located in line I8. Conditionsv of temperature'and pressure in evaporator I9 are controlled to effect vaporization and passage overhead of constituents suitable for further cracking treatment and llighter products. Suitable baffling means may be provided to assist in the removal of entrained material from said vapors and for fractionation effected by the introduction of reflux through line 2|. The upper portion of evaporator I9 is connected with the lower portiton of a fractionator 22 by means of line 23 provided with a valve 24.

Fractionator 22'is provided with cooling means in the upper portion thereof, for example, a cooling coil 25, to eifectthe fractionation of the vapcrs to permit the separation therefrom of a gas oil condensate, optionally, the separation of a heavy naphtha condensate, and the passage over`' head of a light naphtha distillate'and lighter p-roducts. For example, fractionator 22 may be maintained at a pressure of 25 to 200 pounds per square inch with a top temperature of 250 to 350 F. A trap-out tray 2t may be provided at an intermediate point in the fractionator 22 to effect the collection of a heavy naphtha condensate.

Line 28 connects the trap-out tray I3 and the inlet of the c'olof heater 5 and is provided with a pumpl 29 to eiTect the passage of virgin gas oil collected in trap-out tray I3 through the coil of heater 5'.

In heater 5 the virgin gas oil is subjected to suitable cracking conditions of'temperature and pressure to effect a relatively high rate vof conversion to gasoline constituents. When cracking to the extent that the conversion products contain 25% or more of 420 end point gasoline the virgin gas oil may be heated at a pressure of 500 to 2000 pounds per square inch or more with a final temperature of 850 to 1050 F. For example, the virgin gas oil may be heated under a pressure of 500 pounds per square inch to an exit temperature of 950 F. with the contact time regulated to effect the desired degree of conversion.

The products ofthe cracking of the virgin gas oil in heater 5 may be discharged therefrom through line 30 whichk connects with the lower portion of an evaporator 3l whereby the cracked products are introduced into the evaporator 3l for separation thereof into vapors and liquid residue. lOne ormore valves 32 and 33 may be provided in line'30 to effect any desired reduction in pressure on the cracked products. Conditions of temperature and pressure in the evaporator 3| are maintained to` effect vaporization and passage overhead of constituents' suitable for further' of entrained material from the vapors in the up? Cil per portion of evaporator 3| and for fractionation effected by means of reflux introduced at the top of evaporator 3| through line 34.

The upper portion of evaporator 3| is connected with the lower portion of a fractionator 35 by means of line 36 through which the vapors passing overhead from evaporator 3| are introduced into the fractionator 35. Fractionator 35 is provided with cooling means in the upper portion thereof, for example, a cooling coil 38 to effect fractionation of the vapors and permit the separation therefrom of a gas-oil condensate and, optionally, the separation of the heavy naphtha condensate and the passage overhead of a light naphtha distillate and lighter products. For example, fractionator 35 may be maintained at a pressure of 25 to 250 pounds per square inch with a top temperature of 250 to 350 F. A trap-out tray 39 may be provided at an intermediate point in the fractionator 35 to effect the collection of a heavy naphtha condensate.

Line 4| connects transfer lines |8and 30 whereby the cracked products from heaters 4 and 5 may be combined for common treatment in evaporator 3|. Valve 42 is provided in line 4| whereby the distribution of cracked products from heater 4 between evaporator I9 and evaporator 3| may be controlled by manipulation of valves 20 and 42.

Line 43 connects lines 23 and 36 whereby the vapors passing overhead from evaporator |9 may be combined with vapors passing overhead from evaporator 3| and the combined vapors introduced into fractionator 35 for common treatment therein. A valve 44 is provided in line 43, and this valve, together with valve 24, permits the desired distribution of vapors from an evaporator I9 between fractionators 22 and 35.

Line 45 connects the lower portion of fractionator 35 with the inlet of the coil of heater 6 whereby condensate collected in the lower portion of fractionator 35 may be treated in heater 6. Pump 46 is provided in line 45 to effect the passage of the condensate through the coil of heater 6. Line 41 connects the lower portion of fractionator 22 with line 45 whereby al1 or a portion of the condensate collected in the bottom of fractionator 22 may be combined with the condensate from fractionator 35 for common treat ment in heater 6.

In heater 6 the condensate is subjected to cracking conditions of temperature and pressure to effect substantial conversion to lighter products including gasoline constituents. Preferably, however, the condensate in heater 6 is subjected to a lesser degree of conversion than the gas oil in heater 5 because of the nature of the condensate constituting the fresh feed to heater 6. The condensate in heater 6 may be heated at a pressure of 50 to 400 pounds and at a temperature of 875 to 1100 F. For example, the condensate may be heated under a pressure of 200 pounds per square inch to a final temperature of 900 to 950 F. to effect a 10% to 25% conversion to gasoline constituents.

The products of the cracking treatment in heater 6 are discharged therefrom through line 48 which connects the outlet of the coil of heater 6 with the lower portion of an evaporator 49 whereby the cracked products from heater 6 may be introduced into evaporator 49 to effect separation thereof into vapors and liquid residue. Line 50 connects line 48 with the lower portion of evaporator 3| whereby all or a portion of the cracked products from heater 6 may be introduced into evaporator 3| for separation therein. Valves 5| and 52 are provided in lines 48 and 50, respectively, to permit the desired reduction in pressure on the cracked products and to permit any desired distribution of said cracked products to evaporators 3| and 49.

The evaporator 49 is controlled to effect vaporization and passage overhead of constituents suitable or desired for further cracking treatment and lighter products. Suitable baling means may be provided in the upper portion of evaporator 49 to assist in the removal of entrained material from the vapors and to permit fractionation by means of reux introduced at the top of the vessel through line 98.

The upper portion of evaporator 49 is connected with the lower portion of a fractionator 53 by means of line 54 provided with a valve 55 whereby vapors passing overhead from evaporator 49 are introduced into fractionator 53. Line 56 connects line 54 with the lower portion of the fractionator 35 whereby vapors passing overhead from evaporator 49 may be partially or entirely introduced into fractionator 35 for fractionation treatment therein in the manner described. A valve 51 is provided in line 56, and by means of this valve and valve 55 any desired distribution of the vapors to fractionators 35 and 53 may be effected. Fractionator 53 is operated to effect the fractionation of the vapors and separation therefrom of a desired condensate and the passage overhead of a desired distillate and may be maintained at a pressure of 25 to 250 pounds per square inch with a top temperature of 350 to 450 to effect the desired fractionation. A cooling coil 58 or other suitable cooling means may be located in the upper portion of fractionator 53 to effect the desired temperature control.

Line 60 connects the lower portion of fractionator 53 with line |4 and is, provided with a pump 6| whereby condensate collected in the bottom of fractionator 53 may be combined with the heavy naphtha passing through line I4 to the reforming treatment in heater 4. Line 62 connects line 60 and transfer line 30, preferably after at least one reduction in pressure whereby all or a portion of the condensate in line 60 may be diverted therefrom for admixture with the hot products of conversion from heater 5 to cool said hot products and arrest cracking. Valves 6,3 and 64 are provided in lines 60 and 62, re-

spectively, to permit any desired distribution of condensate between heater 4 and transfer line 30.

Line 65 connects line 60 with the upper portion of fractionator 35 whereby all or a portion of the condensate from fractionator 53 may be introduced into fractionator 35 as reflux medium. Valves 66 and 61 are provided in lines 60 and 65, respectively, to permit any desired distribution of condensate between line 60 and line 65.

As an alternative method of handling the gas oil condensate in the base of tower 53, it might pass through line |00 to heat exchanger |0| where it passes in indirect heat exchange with incoming cold crude and serves to preheat the latter before its entrance to heater 3. Line |02 conducts the gas oil condensate from heat exchanger |0| to a tank |03 where it may mix with stocks of a similar character from sources not shown. From tank |03 the gas oil may pass through line |04 and pump |05 to a heat exchanger |06 located on the transfer line 48 from heater 6; or all or a part thereof may be diverted through line |09 to line 62 for admixture in transfer line 30 as described; or all or a part thereof may be diverted through line |I| to line 65 for introduction into fractionator 35 as de` scribed. Valves IIO, I I2 and II3 are provided in lines |09, III and |04, respectively, to effect the desired distribution. After acquiring heat in eX- Y changer |06 the gas oil passes through line |01 back into line 60 through which it may be passed to the entrance of heater 4 as previously described.

The liquid residue from evaporators I9, 3| and 49 may be withdrawn therefrom through lines 68, 69 and 10, respectively, for treatment elsewhere for the recovery of valuable constituents therefrom or for use as fuel.

The uncondensed gases passing overhead from iiash tower 8 and fractionators 22, 35 and 53 are withdrawn therefrom through lines 1I, l2, I3 and 14, respectively, and passed through coolers l5, 16, 'l1 and i8 to effect liquefaction of gasoline constituents therein. The condensate thus obtained is introduced into collectors '19, 80', 8| and 82, respectively, for separation of uncondensed gases. The gases may be withdrawn from the said collectors and from the system through lines 83, 84, 85 and 86. The resulting gasoline condensates may be separately withdrawn from the collectors through lines 81, 88, 89 and 90, respectively; or all or a portion of any or all of the gasoline condensates may be withdrawn from the collectors through lines 9|, 92, 93 and 94 which connect with a common line 95 whereby any gasoline fractions withdrawn through lines 9|, 92, 93 and 94 may be blended as desired.

Line 96 connects trap-out tray 39 with line I4, and line 91 connects trap-out tray 26 with line 96 whereby heavy naphtha collecting in these trapout trays may be passed'wholly or in part to admixture with the heavy naphtha from trap-out tray I2 and subsequent reforming treatment in heater 4.

It is to be understood that the various hot products produced in the system may be cooled intermediate or prior to further treatment by suitable cooling means not shown.y For example, suitable cooling means may be provided to eiect reduction in temperature of the cracked products in lines I8, 4|,30,50or48. t

Fractionating towers 8, 22, and 53 may be provided with suitable gas and liquid contactl or more of heaters 4, 5 and 6.

Separate draw-off means may be provided for withdrawing intermediate products from the system as required by variationsy in the process. Such means are not shown in the drawing for simplicity of illustration.` Itis obvious, however, that the invention is not limited, for example, to the treatment of all the'virgin gas oil from trapout tray I3 or the return to the system for further.

treatment of all the condensate from fractionator 53. Any desired proportion of these and other intermediate products may be employed for further treatment, as required by the operation of the process, and'it is to be understood that the invention is not limited by the mere absence of means for suchseparate draw-off in the drawing.

According to alpreferred modification of the invention heavy naphtha from 'trap-out tray I2 is introduced into the coil of heater 4 together with relatively refractory cycle gas oil from line 60, and the combined stream is subjected to elevated conditions of temperature and pressure to effect reforming of the heavy naphtha and cracking of the cycle gas oil to lighter products including gasoline constituents. For example, the combined stream may -be heated to a temperature of 1000 F. at a pressure of 500 pounds per square inch for a time sucient to effectl 15 to 20% conversion of the cycle gas oil to gasoline constituents. i Reduced crude from the bottom of'tower is passed through line I6 and introduced'into the coil of heater 4 at a point or points substantially removed from the inlet of the coil whereby the above-mentionedv combined stream is subjected to cracking conditions for a time sucient to effectv substantial conversion prior yto the admixture therewith of the reduced crude from line I6. The merged products are thereafter passed through theremainder of the coil of heater 4 under temperature and pressure conditions suflicient to effect conversion of thereduced crude vto lighter products'including gasoline constituents of high anti-knock value and a substantial proportion of products above the gasoline boiling range. For example, the merged stream may be heated to a temperature of 875 to 900 F. while being maintained at the same pressure.

The *cracked products from heater 4 pass through line I8 to' evaporator I9, the pressureA being reduced to that of the evaporator by means of valve 20. Evaporator I9 is maintained at pressure and temperature conditions suitable to effect vaporization overhead of constituents suitable for furthercracking treatment and the separation of a residue suitable for fuel. Forexample, the evaporator I9 may be maintained at a pressure of '75 pounds per square inch With a bottom temperature of 750 to 800 1T'.V and a top temperature of 650 to 750'F. 'Ihe liquid residue .is withdrawn through line 68, and the vapors pass overhead through line 23 for introduction into fractionator 22. In fractionator 22 conditions of temperature and pressure are maintained to effect condensation of a suitable cycle stock which collects in the bottom of fractionator 22, therecovery of a heavy naphtha condensate and the collection thereof in trap-out tray 26 andthe passage overhead of vapors containing light naphtha and lighter constituents. For example, vfractionator 22 may be maintained with a bottom temperature of '525 to 600 F. and a top temperature of 300 F. at a pressure of 75 pounds per square inch.

Virgin gas oilfcollected in trap-out tray I3 is introducedinto the inlet of the coil of heater 5 through line 28r and is subjected in heater 5 to temperature and pressure conditions suflicient to effect substantial conversion to lighter products. For example, the virgin gas oil may be subjected to a temperature of 900 to 950 F. at a pressure of 400 pounds per-square inch for a time sufiicient to effect 25 to 30% conversion to gasoline constituents. l

The cracked products from heater 4 are withdrawn through line 30 for introduction into evaporator 3| wherein temperature and pressure conditions are maintained to effect vaporization of constituents suitable for further cracking into lighter products and the separation of a liquid residue suitable as fuel. For example, evaporator 3D may be maintained at a pressure of 75 pounds per square inch, the reduction in pressure from heater 5 being effected by means of valve 32 and/or valve 33. To assist in the desired vaporization a temperature of 750 to 800 F may be maintained in the base of evaporator 3l, and the top held at 650 to '750 by means of reflux.

The liquid residue from evaporator 3I is withdrawn through line 69, and the vapors pass overhead through line 36 for introduction into fractionator 35.

In fractionator conditions of temperature and pressure are` maintained to effect the passage overhead of vapors including light naphtha and lighter products, the collection in the bottom of fractionator 35 of a condensate suitable for further cracking treatment and the recovery of a heavy naphtha condensate and its collection in trap-out tray 39. For example, fractionator 35 may be maintained at a bottom temperature of 525 to 600 F. and a top temperature of 300 F. at a pressure of 75 pounds per square inch.

The heavy naphtha collected in trap-out trays 26 and 39 is withdrawn therefrom through lines 96 and 91 and combined with the heavy naphtha from trap-out tray I2 for passage to the abovedescribed reforming treatment.

The cycle condensate collected in the bottom of fractionator 35 is withdrawn therefrom through line for introduction to the inlet of the coil of heater 6. The cycle condensate collected in the bottom of fractionator 22 is withdrawn therefrom through line 4l and combined with the condensate passing through line 45 to heater -6. In heater 6 the condensate passing through the coil thereof is heated under temperature and pressure conditions sufficient to effect conversion thereof to lower-boiling products including gasoline constituents. For example, the materials passing therethrough may be heated to a temperature of 1000 F. at a pressure of 400 pounds per square inch for a time suiiicient to effect 15 to 20% conversion to gasoline constituents.

Cracked products from heater 6 are Withdrawn v therefrom through line 48 and introduced into evaporator 49 wherein conditions of temperature and pressure are maintained to effect vaporization of constituents suitable for further cracking treatment and lighter products and the separation of a liquid residue suitable for use as fuel. For example, evaporator 49 may be maintained at a pressure of '75 pounds per square inch, the reduction in pressure from heater 5 being effected by means of valve 5I and with a bottom temperature of 750 to 800 F.

The liquid residue separated in evaporator 49 is Withdrawn therefrom throughline 1, and the vapors passing overhead are Withdrawn through line 54 for introduction into` fractionator 53 which is maintained under pressure and temperature conditions suitable to effect the condensation of constituents above the gasoline boiling range and the passage overhead of vapors including gasoline constituents and lighter products. For example, fractionator 53 may be maintained with a bottom temperature of 90 F. and a. top temperature of 550 to 625 F. at a pressure of 75 pounds per square inch.

'I'he condensate collected in the bottom of fractionator 53 is Withdrawn therefrom through line for admixture With the heavy naphtha in line I4 and passage therewith Ithrough the coil of heater 4. The condensate may be passed directly to heater 4 or preliminarily may be passed through heat exchangers IOI and |05 as described.

The vapors passing overhead through lines 1I, 'I2 and 'I3 are treated as described above to effect the separation and collection of the gasoline constituents therein which may be separately collected or blended in the manner described above.

According to another preferred modification of the invention the heavy naphtha passing through line I4 is passed through the first part of the coil of heater 4 and subjected to reforming conditions of temperature and pressure Without the admixture therewith of condensate from line 60. Reduced crude is introduced through line I6 for cracking treatment as described above, and the cracked products are passed through linesy I8, 4I and 30 for introduction into evaporator 3I for treatment therein in the manner described in connection with this evaporator. Virgin gas oil is subjected to conversion conditions in heater 5 in the manner described, and cycle condensate from line 60 is diverted through line 62 for admixture with the conversion products from heater 5 in line 30 with or Without reduction in pressure by means of valve 33 to effect cooling of the cracked products and to arrest cracking. The combined products are then introduced through line 30 into evaporator 3I for treatment therein with further reduction in pressure, if necessary, by means of valve 32. If desired all or a portion of the condensate from fractionator 53 may be introduced as reflux into fractionator 35 through line 65. If desired, in operating in accordance with this modification the use of evaporator 49 and fractionator 53 may be omitted, the cracked products from heater 6 being passed through lines 48 and 50 for introduction into evaporator 3I for treatment therein; or only fractionator 53 may be omitted, the evaporator 49 being utilized to effect collection of a separate fuel through lines 'I0 and the vapors being introduced into fractionator 35 through line 56.

In either of the preferred modifications the use of evaporator I9 and fractionator 22 may be avoided by the introduction of the cracked products from heater 4 into evaporator 3I; or only fractionator 22 may be omitted in which case the vapors from evaporatorv I9 are combined with those from evaporator 3I by passage through line 43. The use of separate evaporators I9 and 3 I, however, is useful in developing separate fuels of desired differing characteristics.

The present invention, as exemplified in the first-described preferred modification, permits the treatment of a plurality of oils of differing boiling ranges such as the various fractions resulting from distillation of crude oil to effect maximum production of gasoline products of high anti-knock value under conditions of maximum efficiency. The cracking of the reduced crude by admixture with the totally or partially reformed heavy naphtha permits a more drastic treatment of the reduced crude than is feasible in the treatment of this material alone and the production therefrom of gasoline constituents of high anti-knock value at the same time that substantial quantities of heavier products suitable for further conversion are obtained. The separate cracking of the virgin gas oil permits the relatively drastic treatment of this material to effect substantial conversion and production of a high percentage of gasoline constituents of high anti-knock value. The cycle stocks from the reforming treatment and the cracking of the virgin gas oil and gas oil constituents from the cracking of the reduced crude are eii'iciently treated in heater S Wherein they are subjected to the conditions of temperature and pressure most suitable to effect substantial conversion to gasoline constituents of high anti-knock value under conditions of maximum efficiency for such material. The condensate collected in the bottom of fractionator 53 ordinarily Will comprise materials which have resisted cracking in passage through heaters 5 and f5 and Will therefore be relatively refractory in character. This material is advantageously treated by combining it with the heavy naphtha to be reformed in heater 4 wherein it will be subjected to drastic conditions of temperature and pressure necessary to eiect cracking and production of gasoline constituents of high anti-knock value.

According to the second preferred modication condensate recovered in fractionator 53 is returned to the system for further treatment, and constituents suitable for further conversion treatment recovered in fractionator 35 are passed for cracking ltreatment in heater Ei Wherefore complete conversion or the charge to the system to nal products is accomplished.

These and other advantages are apparent from the foregoing description which has been made with reference to specific embodiments of the invention. It is to be understood, however, that the invention is not limited by such specic reference but that the advantages claimed for this invention reside in other modifications and embodiments Which may be beyond the physical limitations of the apparatus described.

I claim:

1. The method of treating hydrocarbon oil that comprises distilling crude petroleum to produce 'therefrom a loW boiling fraction comprising gasoline constituents, a high boiling fraction and an intermediate fraction higher boiling than gasoline, passing said 10W boiling fraction through an elongated cracking zone under superatmospheric pressure While applying heat thereto to subject said fraction to reforming temperature and effect conversion of gasoline constituents into constituents of increased anti-knock value, introducing said high boiling fraction into said elongated cracking zone intermediate the ends products from the elongated cracking zone into vapors and residue and fractionating the vapors to separate a desired gasoline product from higher boiling reflux condensate, directing said intermediate fraction to a second cracking zone and subjecting it therein to cracking conditions of temperature and pressure to eiTect conversion into gasoline constituents, separating the resultant cracked products into vapors and residue, fractionating the separated vapors to form a distillate comprising gasoline and a reflux condensate, combining the latter reux condensate with aforesaid higher boiling reflux condensate and advancing the mixture to a third cracking zone wherein it is subjected to cracking conditions of temperature and pressure to effect conversion into gasoline constituents, separating the resultant cracked products from the third cracking zone into vapors and residue and fractionating the separated vapors to recover a desired gasoline product.

2. The method of treating hydrocarbon oils that comprises distilling crude petroleum to separate vapors from residue and fractionating the vapors to forma low boiling fraction comprising gasoline constituents and a higher boiling fraction, passing said low boiling fraction through an elongated cracking zone under superatmospheric pressure while applying heat thereto to subject said fraction to reforming temperature and effect conversion of gasoline constituents into constituents of increased'anti-knock value, introducing said residue into said elongated cracking zone intermediate the ends thereof and into intimate mixture with the stream o f products undergoing reforming therein to thereby raise the residue to a desired crackingtemper- `ature and subject it to cracking during the passage of the resultant mixture through the remainder of the elongated cracking zone, separating the resultant cracked products from the elongated cracking Zone into vapors and residue,

' directing said higher boiling fraction to a secand pressure to eiTect conversion into gasoline constituents, separating the resultant cracked products from the third cracking zone into vapors and residue, and fractionating the separated Vapors to form a distillate comprising gasoline.

GEORGE ARMISTEAD, J R. 

